Chlorobium chlorochromatii, originally known as Chlorobium aggregatum, is a symbiotic green sulfur bacteria that performs anoxygenic photosynthesis and functions as an obligate photoautotroph using reduced sulfur species as electron donors.

Hydrogenases in Clostridium and other bacteria work primarily to produce hydrogen, while hydrogenases in photosynthetic bacteria work toward hydrogen uptake. Hydrogen-producing efficiency is known to be higher in hydrogenase-deplete strains of photosynthetic bacteria.

Nitrosomonas are rod-shaped chemolithoautothrophs with an aerobic metabolism. While they do not grow by photosynthesis, their unusual metabolic behavior involves burning ammonia with oxygen. Long, thin membranes inside the bacteria’s cell use electrons from ammonia’s nitrogen atom to produce energy.

Anoxygenic photosynthetic bacteria are found in four different phylogenetic groups, which contain different photosynthetic systems: the purple bacteria, two phyla of green photosynthetic bacteria (Chlorobiaceae or green sulfur bacteria, and Chloroflexus or green non-sulfur bacteria), and the Gram-positive Heliobacteria …

They live in various habitats including salt and freshwater aquatic environments, wet soil, or on moist rocks. Photosynthetic algae known as phytoplankton are found in both marine and freshwater environments. Most marine phytoplankton are composed of diatoms and dinoflagellates.

Since then, chemosynthetic bacterial communities have been found in hot springs on land and on the seafloor around hydrothermal vents, cold seeps, whale carcasses, and sunken ships.

Putative fossilized microorganisms were discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec, Canada, that may have lived as early as 4.280 billion years ago, not long after the oceans formed 4.4 billion years ago, and not long after the formation of the Earth 4.54 billion years ago.

Animals such as scaly-foot gastropods (Chrysomallon squamiferum) and yeti crabs (Kiwa species) have only been recorded at hydrothermal vents. Large colonies of vent mussels and tube worms can also be found living there. In 1980, the Pompeii worm (Alvinella pompejana) was identified living on the sides of vent chimneys.

They become inactive when seafloor-spreading moves them away from the rising magma or when they become clogged. Some vent fields may remain active for 10,000 years, but individual vents are much shorter-lived.

In 1977, scientists discovered biological communities unexpectedly living around seafloor hydrothermal vents, far from sunlight and thriving on a chemical soup rich in hydrogen, carbon dioxide, and sulfur, spewing from the geysers. …

Found embedded in crystal, the structures seem to be fossils formed around hydrothermal vents as much as 4.28 billion years ago. Stalks of iron-rich minerals, each a fraction the size of an eyelash, may be evidence of the earliest life-forms to inhabit the newborn planet Earth.

Bacterial Diversity. The most abundant bacteria in hydrothermal vents are chemolithotrophs. These bacteria use reduced chemical species, most often sulfur, as sources of energy to reduce carbon dioxide to organic carbon.

By creating protocells in hot, alkaline seawater, a research team has added to evidence that the origin of life could have been in deep-sea hydrothermal vents rather than shallow pools. Some of the world’s oldest fossils, discovered by a UCL-led team, originated in such underwater vents.

Hydrothermal vents form at locations where seawater meets magma. A venting black smoker emits jets of particle-laden fluids. The particles are predominantly very fine-grained sulfide minerals formed when the hot hydrothermal fluids mix with near-freezing seawater.

Studies that track how life forms have evolved suggest that the earliest life on Earth emerged about 4 billion years ago. That timeline means life almost certainly originated in the ocean, Lenton says. The first continents hadn’t formed 4 billion years ago, so the surface of the planet was almost entirely ocean.

Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million years ago come entirely from Africa. Most scientists currently recognize some 15 to 20 different species of early humans.